A promising premise, like a promising premiere, doesn’t always mean a promising future. Take “Out of Practice,” please.

Despite the super-high-octane leads – Stockard Channing and the Fonz himself (Henry Winkler) – and a winning team of creators (“Frasier“), the writing just isn’t enough to sustain the laughs on tonight’s second episode.

If you watched last week, you know the show centers on a pair of divorcing docs and their grown kids who are docs, and, well, that’s it.

The couple has three kids: Ben (Christopher Gorham), a 30-year-old marriage therapist (who isn’t an M.D. and is constantly noodged about it by the other four who are M.D.’s); Regina (Paula Marshall), the ER doc/lesbian daughter; and Oliver (Ty Burrell), the show-off, womanizing plastic surgeon.

Jennifer Tilly dusts off the slutty girlfriend act – again – this time as Dad’s slutty girlfriend, a role that she played brilliantly the first time in “Bullets Over Broadway,” and overplayed in “The Women.” (In the original, Joan Crawford was brilliantly subtle as the shop girl with socialite ambitions, while Tilly played it like a loud, slutty, gold-digger.)

Marshall is terrific as Regina (she doesn’t overplay the lesbian hand and is so gorgeous I’m seriously thinking of switching teams), and Channing and Winkler can carry almost any cast. Not so for the rest of the family, specifically the two sons who are so hideously miscast that it’s shocking.

For one thing, in the first episode, a couple in their late 60s are seen coming out of good-boy, bland Ben’s office. Right. Now, not for nothing, but can you imagine a couple that’s been married for 40 years going to a 30-year-old who looks 20 for marriage counseling?

And besides which (and this is the running “joke”) Ben stinks so badly himself at marriage that his wife is leaving him.

Hahahahahahahaha.

And then there’s the woman-

izing plastic surgeon son, Oliver. Wrong. Maybe he’s supposed to be a metrosexual kind of guy, but he comes across – in the words of Ahnald Schwarzenegger – as a fussy girly man. Yes, it worked on “Frasier,” but it doesn’t work here.

If you want to see these stereotypes played to perfection, watch how seamlessly Dylan Walsh and Julian McMahon do it on “Nip/Tuck.”

In tonight’s episode, it’s Ben’s 30th birthday, and Mom-the-cardiologist, who is as obsessive about keeping the family together as my ex- (emphasis on “ex!”) mother-in-law was, makes up a schedule for everyone to follow so that Ben will constantly be surrounded by family. Since his wife, the tree-hugging activist, has left him (who can blame her?), they want him to feel loved. Oy.

Divorces aside, how can they not be a happy family? They have everything a sitcom family wants and needs (that no one in real life ever has): swinging kitchen doors and a convenient coffee shop in which to obsessively meet one another to discuss minutiae until the cows drop dead.

Second-week summary: Good that they’re beginning to think outside the box in terms of family makeup (no, not everyone in America, as “Frasier” proved, is 34 years old with three adorable children) but bad in terms of comedy. These pros deserve better than bad jokes and swinging doors.